U.S. patent number 5,268,983 [Application Number 07/986,682] was granted by the patent office on 1993-12-07 for round, dry, all dielectric, fan out compact optical fiber cable.
This patent grant is currently assigned to Alcoa Fujikura Ltd.. Invention is credited to George B. Anderson, Elbert O. Shiflett, Daniel Tatarka.
United States Patent |
5,268,983 |
Tatarka , et al. |
December 7, 1993 |
Round, dry, all dielectric, fan out compact optical fiber cable
Abstract
A round, compact, optical fiber cable comprises an outer
protective jacket of insulating material having a plurality of
individual bundles of optical fibers within the outer jacket. Each
bundle includes an anti-buckling rod of electrically non-conductive
material and encapsulated by a low modulus material. A plurality of
optical fibers encapsulated also in a low modulus material is wound
on and about the low modulus material encapsulating the rod in a
manner that retards contraction and microbending of the optical
fibers. Each of the bundles includes one or more protective jackets
of electrically, non-conductive material enclosing the plurality of
fibers, anti-buckling rod and encapsulating material. Also, means
are provided for identifying individual bundles and fibers.
Inventors: |
Tatarka; Daniel (Simpsonville,
SC), Shiflett; Elbert O. (Simpsonville, SC), Anderson;
George B. (Simpsonville, SC) |
Assignee: |
Alcoa Fujikura Ltd. (Brentwood,
TN)
|
Family
ID: |
25532655 |
Appl.
No.: |
07/986,682 |
Filed: |
December 8, 1992 |
Current U.S.
Class: |
385/106;
385/103 |
Current CPC
Class: |
G02B
6/441 (20130101); G02B 6/4495 (20130101); G02B
6/443 (20130101) |
Current International
Class: |
G02B
6/44 (20060101); G02B 006/44 () |
Field of
Search: |
;385/102,103,106,109,112,113 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
4645298 |
February 1987 |
Gartside, III |
4702554 |
October 1987 |
Takahashi et al. |
5050957 |
September 1991 |
Hamilton et al. |
5067791 |
November 1991 |
Nishiyama |
5155789 |
October 1992 |
Le Noane et al. |
|
Primary Examiner: Lee; John D.
Attorney, Agent or Firm: Strickland; Elroy
Claims
What is claimed is:
1. A round, dry, compact, electrically non-conductive, optical
fiber cable comprising:
an outer protective jacket of electrically non-conductive
material;
a plurality of individual bundles of optical fibers located within
said jacket, with each of said bundles including an anti-buckling
rod made of electrically non-conductive material encapsulated by a
low modulus material and a plurality of optical fibers encapsulated
by a low modulus material wound on and around the low modulus
material encapsulating said rod in a manner that retards
contraction and microbending of the optical fibers and centers the
anti-buckling rod in the plurality of optical fibers;
with each of said bundles including one or more protective jackets
of electrically non-conductive material enclosing the plurality of
optical fibers, anti-buckling rod, and encapsulating material;
and
multiple strands of high modulus, water absorbing, electrically
non-conductive material located inside the outer protective jacket
and adjacent the jackets enclosing the bundles of optical fibers
wherein the bundles of optical fibers and the multiple strands of
high modulus material are tightly stranded together in a helical
fashion to provide compactness inside the outer protective jacket
and throughout the cable to block water and moisture from traveling
through the cable.
2. The cable of claim 1 including a center strength member made of
a high modulus electrically non-conductive material, with the
bundles of optical fibers being wound on said center member.
3. The cable of claim 2 in which the high modulus material of the
center strength member is jacketed with an electrically
non-conductive material.
4. The cable of claim 1 in which the material of the high modulus
multiple strands is aramid yarn.
5. The cable of claim 1 in which a ripcord for opening the outer
jacket lies under the jacket.
6. The cable of claim 1 in which a ripcord lies under each of the
jackets of the bundles of optical fibers.
7. The cable of claim 1 in which the outer protective jacket
includes an inner wrapping of high strength, electrically
non-conductive tape.
8. The cable of claim 1 in which the material of the outer
protective jacket includes a flame-retardant compound.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to optical fiber cables and
more particularly to round "high count" fiber optic cables
particularly useful for making multiple indoor connections between
equipment and hardware that utilize (receive and send) large
amounts of data transmitted through the fibers.
Present optical fiber technology typically uses individual or very
low count cable (usually less than six fibers) to connect outdoor
cables to central office switching equipment and hardware. Such
individual or low count cables are inadequate since the amount of
indoor connections, fiber counts, and central office racks required
is in the hundreds and thousands, depending upon the demand at a
given location. As a result, indoor locations have become and
typically will become highly congested with cable unless action is
taken to reduce the number of cables without reducing the number of
optical fibers. In fact, the need is to reduce cable numbers while
increasing fiber numbers.
Craftsmanship and the ease of cable handling when connecting fibers
to equipment is proportional to (1) the compactness of the cable
structure, (2) the accessibility to the fibers within each cable
with commonly used craft tools such as strippers that do not nick
the fibers, and (3) the adaptability of enclosures and equipment to
the cable construction. In addition, supplemental identification
techniques must be applied at the location of installation for most
of the present cable designs. Hence, for the high count fiber
cables, identification of each fiber becomes highly important in
the fiber connection and termination process.
And, any new design is obviously more cost effective if existing
cabling machinery can be used in making the new cable, as opposed
to the use of specialized and dedicated equipment.
Hence, there are real needs for flexible optical fiber cables that
can handle substantial amounts of information while remaining
compact in size. As explained above, indoor office space is often
unavailable for a substantial amount of cabling. When space is
found, cables are snaked through and around equipment in a manner
that requires a substantial amount of bending so that the fiber
optics of the cable are subject to substantial bending and flexing.
Any bending of the optics reduces the cables ability to conduct
light and therefore can affect the ability to serve its purpose,
which is the rapid transmission of substantial amounts of
information and data in the form of light pulses.
Anti-buckling means in the fiber optic art, which can also serve as
strain relief means for the more delicate optics, are known and
have been the subject of patent disclosures, such as U.S. Pat. No.
4,269,024 to Ashpole et al and U.S. Pat. No. 5,101,467 to Bernard.
Ashpole et al are concerned with strength (strain relief) members
per se, while Bernard shows a cable primarily designed for outside
pedestals located near ground level to receive underground cabling.
Since the Bernard cable is for outdoor, underground use, the cable
has a substantial amount of protective armoring.
In providing a cable for multiple connections to assorted
equipment, each fiber within the cable must be accessible in a
manner that leaves adjacent fibers intact, i.e., when one subunit
or bundle of fibers is connected to one item of equipment, the
remaining bundles need to remain in tact for use at adjacent and/or
other locations and equipment. In other words, when the outer
jacket of a cable is opened to obtain access to subunits of fibers,
the remaining subunits need to remain intact so that they can be
directed and connected to other related or unrelated equipment. All
of this, of course, requires an outer jacketing system that permits
easy access to the subunits within the jacket system, and subunits
with jackets that maintain the subunits intact when the main, outer
jacket is opened.
SUMMARY OF THE INVENTION
The above concerns are met by the cable of the present invention in
which bundles or subunits of optical fiber cables are contained in
an outer jacket of an insulating material, with each of the bundles
themselves having a protective jacket. The protective jacket of
each bundle contains a substantial plurality of optical fibers,
which it maintains as a unit until the jacket is opened for access
to the fibers. Each optical fiber is coated with a low modulus
material that permits easy removal of each fiber from a center,
dielectric rod and strength member which is also encapsulated with
a layer of low modulus material.
Within the confines of the outer jacket and between the outer
jacket and inner jacket of the individual bundles are strands of an
insulating yarn material that provide additional strength and
strain relief for the optics. Further, the material of yarn is
preferably one that prevents the migration of water and moisture
down the length of the cable and thereby maintains the interior of
the cable dry. In this manner, no water resistant filler material
is needed within the cable to prevent ingress of moisture and
water. Such filler materials are generally greasy and make it
difficult to work with the individual fibers in the process of
connecting the fibers to terminals and equipment.
The optical fibers are wound on the rod in a manner that ties them
to the rod so that the fibers resist contraction and microbending.
This is effected by the low modulus material encapsulating the
fibers and rod, as explained in detail below.
With individual "packaging" of the fiber bundles or subunits, when
the outer jacket is opened to obtain access to the bundles, and
only one bundle is needed for the purposes at hand, the other
bundles remain in tact and thus ready for use when and where
needed.
The outer and inner jackets can be opened with a ripcord embedded
in the jackets, as shown in FIG. 1 of Applicants' drawings.
The subject cable is an all dielectric insulating cable such that
no electrically conductive elements are present that would be
available for the conducting of high voltage transients into the
equipment and apparatus to which the fiber optics are
connected.
BRIEF DESCRIPTION OF THE DRAWINGS
The advantages and objectives of the invention will be best
understood from consideration of the following detailed description
and the accompanying drawings in which:
FIG. 1 is a cross-sectional view of a high count cable containing
three bundles or subunits of eight fiber optics, the cable being
constructed in accordance with the principles of the invention;
FIG. 2 is a cross-sectional view of a high count cable having
twelve bundles or subunits of eight optical fibers, again
constructed in accordance with the principles of the invention;
and
FIG. 3 shows schematically means for placing indicia on a bundle
for identification purposes.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to the drawings, FIG. 1 thereof shows in cross
section a round, all dielectric cable 10 comprised of three round
bundles or subunits 12 of optical fibers 14, the number of fibers
(eight) in each subunit, and the total number of fibers in the
cable (twenty-four) being given by way of example only.
Cable 10 includes an outermost jacket 16 of insulating material,
such as a PVC riser compound, and a wrapping of high strength
insulating tape 18, such as polyethylene terephthalate, disposed
about the combination of the three optical bundles 12. If the cable
is used in an outdoor environment, then riser or plenum (flame
retardant) compounds may not be necessary. Electrical
non-conductive strands 20 are located between the wrapping 18 and
bundles 12 to provide strain relief for the optics of the bundles
and preferably to provide absorption of any water or moisture that
might enter the interior of the cable. A preferred material for
strands 20 is a water absorbing aramid yarn.
The bundles 12 and yarns 20 are tightly stranded together in a
helical fashion to provide a compact construction. An appropriate
diameter for cable of FIG. 1 is 6.9 mm, while the diameter of each
bundle is 2.7 mm.
It will be noted in FIG. 1 that the strands or yarns 20 occupy a
substantial portion of the area or space between bundles 12 and
wrap 18. In this manner, the strands will tend to absorb
substantially all water and moisture in the interior of the cable.
This is advantageous in that the interior is otherwise free of
water repellent fillers so that the optics 14 remain free of
contamination by filler materials, thereby easing the process of
the connecting fibers to their destined terminals and equipment,
i.e., filler materials are generally greasy substances that must be
wiped or otherwise removed from the fibers before they can be
properly connected to terminals, hardware, etc.
As shown, each bundle 12 comprises a plurality of optical fibers 14
individually coated and enclosed with a layer of electrically
non-conductive low modulus material 22 and helically applied to a
layer of electrically non-conductive low modulus material 24
located on and encapsulating a rod 26 of electrically
non-conductive material. A preferable material of the rod is fiber
reinforced plastic, while the low modulus material of layers 22 and
24 is a relatively soft silicone rubber. An appropriate thickness
for layers 22 and 24 is simply that amount of material sufficient
to completely surround and encapsulate the rod and optical fibers.
The rod is a relatively stiff structure that does not buckle when
the cable is handled and bent, thereby protecting the fibers from
microbends and outright breakage. Yet, the material of the rod is
flexible to the degree that the bundle and the overall cable can be
manipulated into corners and around equipment, as needed.
The low modulus material of the layers provided on the fibers and
rods causes the fibers and rods to adhere together so that the
fibers are "fixed" to the rods. Such adherence of the fibers to the
rods prevents microbending of the fibers that can occur with
contraction of the cable d unit caused by temperature changes
because the center rods and fibers have similar coefficients of
thermal expansion.
Also, because of the relative softness of the material of layers 22
and 24, individual fibers are easily removed from center rod 26 and
the material easily removed from the individual fibers for
connecting the fibers to terminals and hardware. The coating is
removed with commonly used craft tools that do not nick the
fibers.
The fibers, rod, and low modulus layers of each subunit 12 are
bundled together by a protective jacket 28. The material of this
jacket can also be a PVC riser compound, though other flame
retardant materials can be used.
Access to bundles 22 can be provided by a ripcord 30 of strong
insulating material such as nylon lying underneath the outer jacket
16. In the Figures, the ripcords are somewhat enlarged for purposes
of illustration. In real life, the ripcords are quite small in
cross section with the outer jacket material formed over them.
Since the fibers within the outer jacket are contained within
separate jackets 28, the opening of the outer jacket 16 and the
unwrapping of tape 18 leaves the bundles intact so that they can be
individually and diversely directed to the separate locations of
equipment and hardware. When the end of each bundle is
appropriately disposed for connection, end portions of inner
jackets 28 can be removed from the fibers to allow connection of
the fibers to the equipment. To this end, each inner jacket can
also be provided with a ripcord 32 lying underneath the inner
jacket.
All of the materials of cable 10, as thus described, are
electrically non-conductive.
Each bundle 12 and each fiber 14 are identified by appropriate
numbers or letters printed or otherwise located on the surfaces of
the fibers or by different colors (or combinations of letters,
numbers, and/or colors). The material of the fibers themselves can
be individually colored, as well as the low modulus layers 22 and
24 and jackets 28. Such identifying indicia can be provided in
and/or on the layers 22, 24, and 28 using known on-line printing
devices. FIG. 3 of the drawings shows diagrammatically such means
35 for applying indicia on a bundle 12. Appropriate means include
ink injection devices and printing cylinders. Printing cylinders
imprint or emboss nomenclature on the jacket of the bundle.
FIG. 2 of the drawings shows a round cable construction having a
144 fiber count, using twelve bundles or subunits of the type shown
in FIG. 1, i.e., with each subunit containing twelve optical
fibers. In FIG. 2, those components that correspond to the
components of FIG. 1 bear the same reference numerals.
In FIG. 2, an electrically non-conductive member 40 is located in
the center of the cable, member 40 providing strain relief
protection for optics 14. The material of this member can be that
of rods 26 but is jacketed with a flexible PVC material 42, for
example, to provide a surface area suitable for stranding the optic
bundles thereover. The diameter of rod 40 is limited in size
because if it is too large, it will not be sufficiently flexible
for the purposes of the invention. Therefore, rod 40 is overcoated
to provide a diameter that will accommodate more optical units
12.
The individual bundles or subunits 12 in FIG. 2 are made of the
same general materials as those in FIG. 1 such that the cable
structure of FIG. 2 is electrically non-conductive and provides all
of the insulating advantages of the cable of FIG. 1. The diameter
of the cable of FIG. 2 is on the order of 15.0 mm. An appropriate
diameter for center member 40 and 42 is on the order of 8.5 mm.
The cable structures shown in FIGS. 1 and 2 of the drawings can be
manufactured with typical well known cabling equipment, as the
structures are round. Specialized and dedicated equipment is not
needed. The means for applying the components of the subunits 12 to
center rod 26 are well known and used extensively in the industry.
The same is true for winding the subunits on center member 40 in
FIG. 2. Hence, capital outlays for making the cables of the
invention are not a concern.
The all dielectric materials of the cable construction of the
invention makes the cable light in weight such that the embodiment
of FIG. 1 does not require a central strength member. Rather, the
subunits 12 are helically wound together with the aramid yarns 20,
the yarns and anti-buckling rods 26 providing more than sufficient
strain relief for optics 14.
While the invention has been described in terms of preferred
embodiments, the claims appended hereto are intended to encompass
all embodiments which fall within the spirit of the invention.
* * * * *